This invention relates to methods and apparatus for ocean mining of manganese nodules.
Manganese nodules are abundant and cover large portions of the ocean floor. An average nodule is about two inches in diameter, has an irregular surface, and contains concentrations of manganese (approximately 25%), copper 1.2%), nickel (1.5%), and cobalt (0.2%). The nodules can be found in water as shallow as one hundred feet and to depths of more than twenty thousand feet. Rich and concentrated nodule fields are found in the Pacific Ocean southeast of Hawaii in 14,000 to 18,000 feet of water. The nodules rest at the surface of the ocean floor, even though they may have formed over a time period measured in hundreds or perhaps thousands of years.
The nodules were discovered by researchers aboard the H.M.S. Challenger during an 1873-1876 oceanographic expedition, about one hundred years ago. There were early proposals on underwater mining apparatus and techniques that are also about one hundred years old, but the early proposals were generally directed toward dredging methods. Picking up small nodules on the ocean floor in deep ocean (where the most concentrated fields of nodules occur) by dredging, and then raising the nodules more than ten thousand feet to the surface, is difficult to accomplish efficiently with dredging techniques.
Some more recent proposals for deep ocean mining of the nodules have included remotely controlled self-propelled vehicles pre-programmed to operate on the ocean floor. However, to be effective and efficient, a vehicle operating on the ocean floor must have many capabilities. For example, the vehicle must be able to sense and to avoid obstacles, such as large rocks and ditches or crevasses. It should also be able to vary the speed and direction of movement to best suit the local conditions. And the operation of the nodule pick-up and handling mechanism should be variable and controllable as required, etc.